DYNAMIC YOUNG MODULUS AND INTERNAL-FRICTION IN PARTICULATE SIC AL COMPOSITES/

Anelastic behavior of an SiC particulate reinforced aluminum composite has been examined through the measurements of the dynamic Young's mod ulus and internal friction over a temperature range from 25 to 450 deg rees C at frequencies of 0.01, 0.05 and 0.1 Hz. A standard servo-hydra ulic mechanical testing machine equipped with an infrared lamp heater was employed, but the dynamic measurement system therein was especiall y designed by assembling a scanning laser extensometer and a frequency response analyzer for detecting the amplitude and phase lag of strain in response to a sinusoidal lime-varying stress. Two broad peaks of i nternal friction were observed over the ranges 100 to 250 degrees C (L T peak) and 250 to 400 degrees C (HT peak), together with marked decre ases in the dynamic Young's modulus in the same temperature ranges. Fr om a quantitative analysis of the experimental data, it is concluded t hat the HT peak phenomenon is due to grain-boundary relaxation, wherea s the LT peak phenomenon is ascribable to the relaxation caused by str ess-directed interfacial diffusion of Al atoms along the particle-matr ix interface. (C) 1998 Acta Metallurgia Inc.